Tube and sheet heat exchangers with some of the tubes plugged, are often repaired by methods which include steps of removal of plugs from the tubes. A mechanical removal tool was disclosed, for example, in U.S. Pat. No. 4,696,102 issued to Mark A. Overbay, one of the inventors of the instant application, and assigned to the same assignee as the instant application.
The process of electron discharge machining (EDM) is one by which workpiece materials that conduct electricity can be removed from a workpiece by an electric arc. The arc is created by creation of an electrical potential between an electrode of the tool and the conductive workpiece.
Steam generator repair which includes plug removal can be done by electron discharge machining but heretofore the tools for such work have been large and cumbersome. For this reason they have not easily been adapted for remote use as an end effector of a manipulator arm of the type now typically used in nuclear steam generator repairs to minimize worker exposure time to radiation.